Privacy on a phone is not always about keeping everything hidden. Sometimes it is about deciding what you are comfortable showing. That distinction became important while I was building Xsilent, a private Android vault for photos, videos, PDFs, and other personal files. Imagine a simple situation. Someone asks to see the photos from a trip. You unlock your phone, open the collection, and hand the device over for a moment. The first photo is fine. Then comes the familiar gesture: swipe. Ma...